Polysaccharides produced by Actinomyces viscosus may promote adherence of those microorganisms to glycoproteins adsorbed to enamel or exposed root-surfaces. They may inhibit or enhance lectin mediated coaggregation between oral bacteria, and contribute to the bulk of plaque. These polysaccharides can also induce formation of antibodies that may hinder or promote development of dental caries. Although A. viscosus produces several polysaccharides their chemical fine structure remains to be elucidated. Evaluation of their role in the pathogenesis of root surface caries is also lacking, This proposal therefore aims: 1-on the surface of intact A. viscosus cells by quantitative fluorochrome-tagged lectin binding assays which yield information on the nature, number and affinity (Ka) of binding sites; 2- to isolate in purified form, cell wall, cell wall associated and extracellular polysaccharides from T6, T14V and T14Av strains of A. viscosus and characterize their molecular structure by chemical and immunochemical methods; 3- to examine the ability of isolated polysaccharides to serve as antigen inhibit attachment of bacteria to saliva coated hydroxylapatite coated beads and inhibit bacterial coaggregation; 4- to examine the antibody combining site specificity of rat and rabbit polyclonal antibody to isolate A. viscosus polysaccharide antigens; 5- to actively immunize rats with isolated polysaccharide antigens to determine the ability of specific polymers to stimulate suppression or enhancement of disease upon oral infection and 6- to prepare monoclonal rat antibodies against isolated polysaccharide antigens, elucidated their combing site specificity and evaluate the role of specific anti-carbohydrate in modifying implantation and disease in specific pathogen-free rats.